Electrothermic production of boron carbide



Patented June 20, 1939 UNITED STATES PATENT oFFicE ELECTROTHERMIC PRODUCTION OF BORON CARBIDE No Drawing. Application September 4, 1936, Se-

rial No. 99,496. In 1935 '7 Claims.

This invention relates to the production of boron carbide with a low carbon content and has for its object to provide a simple and efficient electrothermic process for this purpose.

In carrying out the invention we first melt down a mixture of boric acid and carbon. The melt thus obtained, which contains about 25% carbon, is next crushed and mixed with about the same quantity of boric acid. This mixture is 10 then heated in an electric-arc furnace or resistance furnace to about the melting point. The boron carbide thus produced with a low carbon content averaging 15-20%, possesses valuable properties, particularly as grinding material, as

15 compared with the product obtained with the first melt.

The designation boron carbide is used herein in the conventional sense, it being immaterial for the purpose of the invention whether the product 20 obtained in any particular case represents a solution of carbon in carbide or the reverse. The process of the invention can also be efiected under a raised pressure as well as with the use of additions which promote the carbide formation 25 and facilitate the melting process. It is also possible to produce mixed carbide in such a manner that to the initial material or the intermediate product there are added metals or their compounds, such as aluminium, titanium, manganese,

30 etc., or their mixtures, suited to the formation of carbide.

Example A mixture of 25 kilograms of boric acid and 35 28 kilograms of charcoal are melted in an electric arc furnace for six hours. After cooling, the heavy block of about kilograms thus obtained is comminuted and mixed with about the same quantity of boric acid. This mixture is thereupon 40 heated in an electric arc or resistance furnace until it melts. About 9 kilograms of boron carbide are obtained with a content of about carbon, which has an extraordinary hardness. Instead of boric acid a chemical equivalent com- 45 pound thereof can be used. The invention claimed is:

Germany September 1'7,

'1. Process for the production of boron carbide, which comprises melting a mixture of carbon and boric acid, comminuting the resulting product and mixing it with substantially the same quantity of boric acid, and melting the mixture a second time.

2. Process for the electrothermic production of boron carbide, which comprises melting a mixture of carbon and boric acid in an electric furnace, cooling and comminuting the resulting product and mixing it with substantially the same quantity of boric acid, and melting the mixture in an electric furnace a second time.

3. Process for the production of boron carbide, which comprises melting a mixture of carbon and boric acid in an electric arc furnace, comminuting the resulting product and mixing it with substantially the same quantity of boric acid and melting the mixture a second time in an electric arc furnace.

4. Process for the production of boron carbide, which comprises melting a mixture of carbon and boric acid containing compounds, comminuting the resulting product and mixing it with substantially the same quantity of boric acid containing compounds and melting the mixture a second time.

5. Process for the production of boron containing carbide, which comprises melting a mixture of carbon, boric acid, metals containing compounds capable of forming carbides, comminuting the resulting product and mixing it with substantially the same quantity of boric acid and metals containing compounds capable of forming carbides and melting the mixture a second time.

6. The process according to claim 1, characterized by adding metallic materials capable of forming carbides to the initial materials.

7. The process according to claim 1, characterized by adding a metallic material capable of forming carbides t0 the intermediate product resulting from the first melting of the mixture of boric acid and carbon.

FRANZ SCI-IROIL. ADOLF VOGT. 

